VIEW ARTICLE

Internal Seed-Borne Nature of Sclerotinia sclerotiorum and Phomopsis sp. and Their Effects on Soybean Seed Quality. J. F. Nicholson , Graduate Research Assistant, Department of Plant Pathology, University of Illinois, Urbana 61801; O. D. Dhingra(2), and J. B. Sinclair(3). (2)(3)Graduate Research Assistant and Professor, respectively, Department of Plant Pathology, University of Illinois, Urbana 61801. Phytopathology 62:1261-1263. Accepted for publication 15 May 1972. DOI: 10.1094/Phyto-62-1261.

Sclerotinia sclerotiorum and Phomopsis sp. (Diaporthe phaseolorum var. sojae) are internally seed-borne in soybean (Glycine max), and may inhibit seed germination in vitro and field emergence. S. sclerotiorum was internally seed-borne in: 30 of 39 lots of Lee 68 seed harvested from six states in 1969 and 1970; eight lots of 1971 Cutler seed from Kentucky; and one lot of Beeson and 17 lots of Amsoy 1971 seed from Illinois. When recovery was more than 25%, in vitro germination and field emergence were reduced. Recovery of S. sclerotiorum from Lee 68 seed was reduced when stored at room temperature (22 ± 3 C) after 6 and 24 months, when compared to samples of the same seed lots stored for 18 months at 3 ± 1 C. Recovery from Cutler seed increased 26% between normal and late harvest periods 30 days apart, but harvest method (machine or hand) appeared to have no effect on percent occurrence of the fungus. S. sclerotiorum was first isolated from seed and pods of field-grown plants at 16 weeks after planting. Phomopsis sp. was internally borne in the following seed lots: 12 of 20 Lee 68 lots harvested in 1970 from five states; eight lots of 1971 Cutler seed from Kentucky; one lot of 1971 Beeson seed; and 17 lots of 1971 Amsoy seed from Illinois. Phomopsis sp. was recovered from less than 25% from any single lot assayed, except for two lots. A reduction in in vitro germination or field emergence was not detected.